1. Field of the Invention
The present invention generally relates to a light-emitting diode package (LED package), and more particularly, to an LED package with high light-emitting efficiency.
2. Description of Related Art
An LED is counted as one of semiconductor devices, and an LED chip is mainly made of compounds of groups III-V, for example, gallium phosphide (GaP), gallium arsenide (GaAs) or other semiconductor compounds. The LED functions to emit light through converting electrical energy into light. I more detail, when a current is applied to an LED, the electrons and the holes in the LED are re-combined for releasing photons so as to emit light. Since an LED emits light not by heating or arc-discharging to be realized, thus, an LED has a long lifetime over a hundred of thousands hours; additionally, no idling time is needed to start operating. In fact, an LED has many advantages, such as fast response speed (about 10−9 second), small size, power-saving, low pollution, high reliability and suitability for mass production; therefore, the LED is widely used in various fields, for example, light sources used in mega-size display board, traffic light, handset, scanner, fax machine, and illumination devices. Due to the light-emitting luminance and the light-emitting efficiency of an LED have been steadily enhanced. It is noted that, white LEDs are capable of being successfully mass-produced now, the LEDs start to be applied in display or illumination products.
FIG. 1 is a schematic cross-sectional drawing of a conventional LED package. Referring to FIG. 1, a conventional LED package 100 includes a lead-frame 110, a light-emitting diode chip (LED chip) 120 and an encapsulant 130. The lead-frame 110 has a surface 110a and the surface 110a is a specular surface for reflecting the light emitted from the LED chip 120. The LED chip 120 is disposed on the lead-frame 110 and is electrically connected to the lead-frame 110. Additionally, the encapsulant 130 encapsulates the LED chip 120 and a part of the lead-frame 110 such that and the rest part of the lead-frame 110 is exposed out of the encapsulant 130 and serves as an external electrode E.
As shown in FIG. 1, the encapsulant 130 comprises a casing 132 and a first light-transmitting portion 134. The casing 132 has a cavity 132a, the LED chip 120 is located in the cavity 132a and the cavity 132a has a side-wall S with a fixed inclination. The light-transmitting portion 134 is disposed in the cavity 132a and joined with the casing 132. The light-transmitting portion 134 encapsulates the LED chip 120 and the part of the lead-frame 110 that is not encapsulated by the casing 132.
As shown in FIG. 1, although the specular surface of the lead-frame 110 reflects light very well, the light emitted from the LED chip 120 and the light reflected by the partial lead-frame 110 encapsulated by the light-transmitting portion 134 might be stayed inside the light-transmitting portion 134 of the encapsulant 130 due to total internal reflections, so as to reduce the overall light-emitting efficiency of the conventional LED package 100.